Sorption of chromium(VI) using modified forms of chitosan beads

Modified forms of chitosan beads were prepared and used for chromium removal from the aqueous solution. The prepared chitosan beads viz., protonated chitosan beads (PCB), carboxylated chitosan beads (CCB) and grafted chitosan beads (GCB) possess enhanced chromium sorption capacities (SCs) of 3239, 3647 and 4057 mg/kg respectively than the raw chitosan beads (CB) which possess the SC of 1298 mg/kg with a minimum contact time of 10 min. The sorption experiments were carried out in batch mode to optimize various influencing parameters viz., contact time, pH, common ions and temperature. The sorbents were characterized by FTIR and SEM with EDAX analysis. The modified chitosan beads remove chromium by means of electrostatic adsorption coupled reduction and complexation. The adsorption data was fitted with Freundlich and Langmuir isotherms. The calculated values of thermodynamic parameters indicate the nature of chromium sorption. A field trial was carried out with water collected from a nearby industrial area. (C) 2010 Elsevier B.V. All rights reserved.